Portable tangent galvanometer



(No Model.) '3 SheetsSheet 1.

. E. WESTON. PORTABLE TANGENT GALVANOMETER.

N0. 403,312. Patented May 14, 1889.

WITNEEEES. INVENTDR. geo W d.www(.' %fn 67% M ymra 'mm maamq N. Prtzns. Phow-Ukhognphur. Waabingtom 0.0.

(No Model.) 4 3 Sheets-Sheet 2.

E. WESTON. PORTABLE TANGENT GALVANOMETER.

N0. 403,312. Patented May 14', 1889.

FIBER.

WITNEESEE I INVENTOR- axwaaakw Dywmd Kile/shanywm ag g w 1g sums Phalo-Lithognphnn Washington. D. c,-

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NITED STATES FFICE.

PORTABLE TANGENT GALVANOMETER.

SPECIFICATION forming part of Letters Patent No. 403,312, dated May 14, 1889. Application filed May 10, 1888. Renewed March 18, 1889. Serial No. 303,818. (No model.)

My invention relates to that class of gal-' vanometers in which the tangent of the angle of deflection of the magnet-needle is proportional to the strength of the current traversing the coils of the instrument.

The object of the invention is to provide a tangent reflecting-galvanometer and a scale for measuring the needle-deflections in a single apparatus in compact portable form, which apparatus, by reason of the principles followed in its construction, shall be accurate and reliable in its determinations.

The principal novel features embodied in the instrument consist in the construction and arrangement of the damping-chamber for preventing undue oscillations of the magnetneedle; in the form of the ring-magnet and its combination with the index-mirror and standard; in the combination of the standard, magnet, and mirror with the scale-chamber located upon the standard, as set forth, and in the various other instrumentalities and combinations entering into the construction of the apparatus, all as hereinafter more particularly described and claimed.

In the accompanying drawings, Figure 1 is an elevation of the instrument. Fig. 2 is a plan view of the same. Fig. 3 is a vertical section. Fig. 4 is a side view, and Fig. 5 a cross-section, of the ring-magnet. Fig. 6 is a vertical section of block containing the damp- Fig. '7 is a face view of one of the sections of said block. Fig.8 is a diagram illustrating the mode of determining the shape of the ring-magnet. Fig. 9 shows a block containing the damping-chamber and having two sight-openings relatively disposed at an angle. Fig. 10 shows a ring-magnet having a central ball in place of a sight-disk.

Similar letters of reference indicate like parts.

' A is a central hollow standard, upon opposite sides of which are fixed supports or brackets L, provided with curved grooves or channels. In said grooves are secured by means of set-screws M the flanged rings J J and the spools D D, of ebonit-e or other insulating material, upon which are wound the coils N of the instrument.

At about the middle of the standard A is an enlargement having a circular bore or opening in which is placed the block E, of diamagnetic metal. In said block is a chamber, g, wherein the magnet-needle F is suspended. The construction and relation of the standard A and coils N is such that when the coils are secured in place upon the stationary brackets L a line joining the centers of the coils intersects the longitudinal aXis of the standard at right angles thereto and passes through the center of the chamber g. The magnet F is disposed in said chamber 9 so that its center coincides with this point of intersection. The construction of the standard and coil-supports, whereby this relation of the coil-centers and position of the needle-center is mechanically secured, is fully described and claimed in another application for Letters Patent, Serial No. 273,517, filed simultaneously herewith by me, to which application reference for further particulars is hereby made.

The cylindrical block E is made of diamagnetic metal, so as to dampen or check the oscillations of the magnet inclosed in its central chamber, g. Said block is divided transversely into halves, and the parts are inserted into the bore of the enlargement of the standard A from opposite sides and are connected together by screws 0, Figs. 1 and 6, dotted lines. The chamber is formed by the juxtaposition of recesses made in the respective halves of the block. Through the central longitudinal axis of the block E is made a slight hole, f, and at one end or at both ends of said aperture an eye-piece or eye-pieces, G, are secured.

Seated in a socket in the upper extremity of standard A is a glass tube, I, at the top of which is a cap, P, through which passes a threaded suspension rod, Q, provided at its lower end with a hook, to which a silk or other suitable fiber, I, is attached. The fiber I supports the ring-magnet F in the chamber g.

I will now explain the shape of the ringmagnet F.

My object is to produce an annular magnet of given width having the greatest possible internal diameter consistent with the dimensions oi"; the chamber g and containing the largest possible mass of metal, by which means I obtain the greatest possible separation of the poles. I accomplish this by determining the shape of the cross-section of the magnet in the manner illustrated by the enlarged diagrannl igS. (Not made to scale.) Here the circle 71. represents the inner periphery of the magnet-chamber g. From the same center, with a radius slightly less than the radius of the circle 71, I draw the are i, which fixes the shape of the outer face of the magnet-ring, and also provides for clearance between said ring-face and the chamber-periphery. The length of this are is limited in accordance with the width (length of the chord of the arc, dotted lines) which it is desired to make the magnet. From the middle point, j, of the are '1; as a center, with the radius equal to the distance of the are extremity from said point, I strike the arc 7r, which determines the shape of the inner periphery of the ring. Finally, I round off the angles of junction formed by the arcs i and in, as in dicated at Z.

Extending across the magnet I is a slender aluminium bar, l), exactly in the center of which is secured a small disk, a. hen the suspending-fiber I coincides exactly with the longitudinal axis of the standard A, the standard then being vertical, and when the coils at the same time are placed in the magnetic meridian, the disk 0. will stand in a plane exactly transverse the sight-hole f, so that on looking at said disk through the eye-piece g a uniform circle of light will appear around it.

Instead of a flat disk, a, secured to the rod 7), described,I may employ a ball or sphere, as shown at a, Fig. 10, and instead of employing a single sight-hol disposed in the axis of block E, I may use two sight-holes, as f f, Fl 8, placed at an angle so that the lines of sight intersect at the center of the globe a. \Vith this construction accuracy of adj ustment is secured when a uniform circle of light appears around the globe at, regarded first through one and then through the other eyepiece, G or G".

In order to avoid weakening the magnetic moment of the needle by alterations in the distribution oi": the mass thereof,which would follow the making of perforations therein for the attachment of a suspension device, I provide a rod, 0, of non-magnetic metal, having arms 6, which are bent around the body of the magnet, as shown, forming a clamp therefor. Inserted longitudinally into the rod 0 is a short rod, (Z, which may be connected to rod (2 in any suitable way, as by a tight fit or a screwthread, and to this red (Z the suspension fiber I is attached. A precisely-similar device consisting of. the rod 0, having arms (2., and the short rod (1 is secured tothcop 'msite side of the magnetring.

To the rod (1 is secured a thin aluminium rod, K, which supports the mirror .lI.

At the lower end of standard A is a projection, R, which enters a socket in the upper central plate, S, of the scale-chamber C. The socket-plate S is supported from the base ol' the scale-chamber by a curved wall,V, and by pillars W. The standard A is also secured to said plate 5 by screws m. The base-plate U is circular, and has a rim or flange, n, on the inner periphery of which a scale is inscribed. The upper side of the scale chamber 0 is closed by an annular glass plate, 0, which surrounds the socket-plate S. At the center of the under side of the base-plate U is a conical projection, 11, which enters a suitablyformed socket in the tripod-stand B, and is secured by a nut, g, which is received upon the fixed threaded rod 1' and bears against the washer s. The tripod B is provided with the usual leveling-screws at the ends of the arms.

At T and T are telescopes arranged in the flange or rim n and disposed ninety degrees apart, or at a distance of forty-five degrees on each side of a line drawn at right angles to the face of the mirror when at rest and meeting the said rim. Consequently when no current is traversing the coils a sight at the mirror through the telescope T shows the telescope T, or rather the zero-point of the scale marked at the latter telescope, and a similar sight through the telescope T shows a second scale-zero marked at telescope '1. By reason of this construction of the scale I obtain a range of measurement equal to one hundred and eighty degrees of are, or ninety degrees of mirror movement.

I do not herein describe in detail nor claim the general construction of scale, telescope, and mirror herein set forth, for the reason that I have fully set forth and claimed the same in another application for Letters Patent filed by me simultaneously herewith, Serial No. 272,634.

It will be observed that the suspended mirror II is wholly inclosed in the chamber 0, and is thus protected from dust and air-currents.

The aperture in the tripod B, which receives the projection I, is made in a boss, i. On the side of this boss is a short toothed segment, 2!. Attached to the under side of the bottom plate, U, are bearings foraworm-screw which engages with said segment. By turning the said screw the stai'idard A may be rotated on its longitudinal axis, and the coils in this way adjusted in the magnetic meridian.

I claim 1. In a galvanometer, in combination with a hollow standard and a vibrating magnet, a removable body of diamagnctic metal sup ported in said standard and having a central chamber wherein said magnet is supported, substantially as described.

In a galvanometer, a dam ping d evicc for the magnet, eonsisti ng oi two separal dc pieces IIO of diamagnetic metal with a recess formed in one face of each piece, the said recesses, when said pieces are in contact, tormin g a chamber for the reception of the magnet, substantially as described.

3. In a galvanometer, in combination with a hollow standard, a removable body of diamagnetic metal supported in said standard and containing a central spherical chamber, and a ring-magnet supported within said chamber, substantially as described.

4. In a galvanometer, in combination with a hollow standard containing a cylindrical transverse opening, two cylindrical bodies of diamagnetic metal placed end to end in said opening and having a chamber formed in their meeting faces, and a magnet supported in said chamber, substantially as described.

5. In a galvanometer, in combination with a hollow standard containing a'cylindrical transverse opening, two cylindrical bodies of diamagnetic metal placed end to end in said opening and having a chamber formed in theirmeeting faces, a meanssuch as screws of connecting said cylindrical bodies together, and a magnet supported in said chamber, substantially as described;

6. In a galvanometer, in combination with a hollow standard, a body of diamagnetic metal supported in said standard and containing a chamber, a ring-magnet supported in said chamber, and a sight aperture extending through said body in line with the center of said chamber, substantially as described.

'7. In a galvanometer, in combination with a hollow standard, a body of diamagnetic metal supported in said standard and containing a central chamber, a ring-magnet supported in said chamber, and two sight-apertures extending through said body in line with the center of said chamber and relatively disposed at an angle, substantially as described.

8. I11 a galvanometer, a ring-magnet needle having a sight disk or ball supported at its center,substantially as described.

9. In a galvanol'neter, in combination with a hollow standard, a body of diamagnetic metal supported in said standard and containing a chamber, a sight-aperture extending through said body in line with the center of said chamber, and a ring-magnet having at its center a sight disk or ball and supported in said chamber, substantially as described.

10. In a galvanometeiyin combination with a standard having a spherical chamber, a ringmagnet supported in said chamber, the outer contour of the cross-section of said magnet being concentric with the periphery of the said chamber, substantially as described.

11. In a galvanometer, in combination with a standard having a spherical chamber, a ring-magnet supported in said chamber, the outer contour of the cross-section of said magnetbeing concentric with the periphery of said chamber, and the inner contour of said cross-section being the arc of a circle struck from the middle point of the arc torming the outer contour and joining the ends of said are, substantially as described.

12. In a galvanometer, a ring-magnet needle, a clamp embracing the body of said magnet, and a support for said magnet connected to said clamp, substantially as described.

13. In a galvanometer, a central hollow standard, a magnet suspended in said standard, a body rigidly connected to and suspended from said magnet, and a scale surrounding said body, substantially as described.

14. In a galvanometer, a base, a circular scalechamber supported thereon and having a scale marked on its inner periphery, a cent al hollow standard supported on said chamber, a magnet suspended in said standard, and a mirror in said scale-chamber and connected to and vibrated by said magnet, substantially as described.

15. In a galvanometer, a central hollow standard, a magnet suspended in said standard, a mirror rigidly connected to and suspended from said magnet, and a circular scalechamber surrounding said mirror, disposed below said standard, and having on'its inner periphery a scale for showing the mirror defiections, substantially as described.

16. In a galvanometer, a central hollow standard, a magnet therein, a mirror vibrated by said magnet, and a scale-chamber secured to said standard and concentric therewith and extending around said mirror, substantially as described.

17. In a galvanometer, a central hollow standard, a magnet therein, coils secured in parallel planes on opposite sides of said standard, and a scale-chamber secured to and surrounding said standard and concentric therewith and arranged below said coils, substantially as described.

18. In a galvanometer, a hollow Vertical standard, a circular horizontal scale-chamber concentric therewith, a magnet suspended in said standard, a mirror suspended from said magnet and entering said chamber, and a base, in combination with means for rotating said standard and chamber about a vertical axis, substantially as described.

19. In a galvanometer, a hollow standard, parallel coils supported on opposite sides thereof, a circular scale-chamber supporting said standard and concentric therewith, a magnet suspended in said standard, a mirror in said scale-chamber and rigidly connected to and suspended from said magnet, a base, and a central pivot on the lower side of said scale-chamber entering said base, in combination with meanssuch as a tangent-screw and segmentfor rotating said standard and scale-chamber upon said pivot, substantially as described.

20. In a galvanometer, a central standard, coils supported thereon, a circular scale-cham ber below said standard, and in said chamber a central support upon which said standard rests, substantially as described.

23. In a gELlVUlOlllOllOl, the combination of 15 the magnet F, rod (2, having clamping-arms e, i'od (Z, and SUSPGIISlOl'l fiber 1, substantially as described.

24. In a gal\anoinoiior, tho combination of tho magnet F, rod having (danip'iagar-ins a, rod d, rod K, and lllll'l'Ol' ll, substantially as described.

HVAnn WES'ION.

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